1. Field of the Invention
The present invention relates to a caster. More specifically, the present invention relates to a swivel caster assembly having an integrally-formed bearing cup for retaining a bearing assembly, wherein the likelihood of contamination of the bearing assembly by a foreign substance is greatly reduced.
2. Description of the Prior Art
Casters are utilized in a wide variety of applications, such as providing mobility for a supported structure including pallets, carriages, bins, chests, carts, trolleys, furniture, scaffolding, and the like. In use, casters are generally characterized as being either furniture, apparatus, transportation equipment, or heavy duty casters.
A caster is either of a rigid type, i.e. non-swiveling, or a swiveling type. In the rigid type, the caster wheel is free to rotate about a horizontal axis but is otherwise fixed with respect to the supported structure. This arrangement allows for translational movement of the caster with respect to a supporting surface on which the caster moves. In the swiveling type, the caster wheel also is free to rotate about a substantially vertical axis relative to the place where it is secured to the supported structure. This allows both translational and rotational movement of the caster with respect to the supporting surface on which the caster moves. Typically, in a swiveling-type caster, the wheel is offset from the vertical axis so as to trail the vertical axis during movement of the supported structure. The present invention pertains to an improvement in a swiveling-type caster.
In certain instances, casters are provided with a motion-restricting, locking device to inhibit and/or prevent swiveling of the caster per se to effect a directional locking feature and/or to prohibit rotation of the caster wheel to effect a braking action.
Factors affecting the design of a caster include operating environment, ease of maintenance, loading, rolling characteristics, maneuverability, and locking features. These factors lead inter alia to caster geometry and size, selection of component materials and surface treatment, size and disposition of the bearing assembly, and the method by which the caster is secured to the supported structure.
U.S. Pat. No. 1,395,484 (Diss) discloses a simple, conventional, top-bearing caster which is generally open and therefore subject to fouling or contamination by a foreign substance.
U.S. Pat. No. 1,861,539 (Lilly) discloses a swivel caster which is designed to reduce the likelihood of jamming of the caster wheel as a result of contamination or fouling by a foreign substance. Although the featured caster provides some protection against contamination, the bearing assembly is not protected.
U.S. Pat. No. 3,964,124 (Crawford) discloses a sealed caster wherein the relatively movable parts, such as the swivel bearing, are sealed by a resilient synthetic material to prevent entry of foreign matter into the bearing. Although the sealed caster provides some protection for the swivel bearing, it is still vulnerable to corrosion because the seal is not watertight.
U.S. Pat. No. 4,554,704 (Raffaeli) discloses a corrosion-resistant caster, designed for use in a corrosive environment, utilizing caster parts having a permanently-bonded, high-lubricity fluorocarbon polymer coating. Although such casters are useful for some applications, the use of coated moving parts is generally not well-suited for casters intended for heavy load applications.
U.S. Pat. No. 4,835,815 (Mellwig, et al.) discloses a caster including a blocking device in the form of a pivoting brake member which restricts movement of the caster wheel relative to the caster frame and movement of the frame relative to its support.
Other conventional casters are disclosed in U.S. Pat. No. 3,691,590 (Drabert), U.S. Pat. No. 4,620,342 (Haussels), and U.S. Pat. No. 4,805,259 (Kassai). U.S. Pat. No. 4,815,161 (Trimmer, et al. ), U.S. Pat. No. 4,941,552 (Screen), and U.S. Pat. No. 4,985,960 (Zun, et al.).
In addition, caster designs are shown in U.S. Pat. No. Des. 308,934 (Howell et al.), U.S. Pat. No. Des. 329,011 (Block), and U.S. Pat. No. Des. 319,384 (Lang).
A useful source of technical information pertaining to caster technology is Wheels and Casters by Verlag Moderne Industrie AG & Co. with the collaboration of Albert Schulte Sohue GmbH & Co. (1992).
Although prior art casters may be well-suited for many varied applications, there is need for an aesthetic, durable caster with a protected bearing assembly that is resistant to fouling due to contamination by a foreign substance, which is capable of being very easily fabricated and maintained, and which lends itself to a broad variety of applications, particularly in the food-service, lodging, and health-care industries where maintaining cleanliness of the caster and supported structure by washing with water and/or a disinfectant solution must be performed on a regular basis.